Field of the Invention (Technical Field)
Embodiments of the present invention relate to feedwells for mineral processing plant thickeners and clarifiers. More particularly, embodiments of the present invention relate to feedwells having a plurality of openings disposed on a lower portion thereof for more uniform distribution of fluids from the feedwell into fluids disposed in a sedimentation chamber (also known as a thickener tank) disposed there below.
Description of Related Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
For a feedwell to provide desirable results, it must permit components to be mixed and retained therein and thus have rather substantial and appropriate fluid kinetics. However, the feedwell should also isolate, to the greatest extent possible, such fluid kinetics from the contents of the sedimentation chamber, while still permitting a sufficient fluid flow rate from the feedwell to the sedimentation tank to accomplish a desired overall feed flow rate.
A typical feedwell is shown and described in U.S. Patent Pub. No. 2011/0079563 (the '563 application), having a single, large outlet as shown in the figures thereof (reference numeral 8). Such feedwells are common and have the characteristic downside of forcing all contents of the feedwell to escape through a single large opening in the bottom. Such a configuration enhances turbulence and creates undesirable flow patterns within the upper portion of the sedimentation chamber within which it is disposed. Although the '563 application seeks to reduce such turbulence by disposing a plurality of fins into the single large opening, such fins themselves disturb the flow of the exiting fluid, thus enhancing the turbulence induced within the sedimentation chamber, which is an undesirable characteristic.
Some inventions, such as that disclosed in U.S. Pat. No. 7,591,946 to Taylor, seek to minimize the induced turbulence by forcibly mixing the contents of its feedwell in a lower portion thereof and forcing the contents of the feedwell to escape therefrom at an upper opening through a Bundt pan shape. By forcing the discharge of the feedwell to be concentrated near a central bottom portion of the feedwell, the flow rate of the discharge is thus comparatively larger than would occur if Taylor instead spread the discharge of the feedwell out over a much larger area.
Like other known feedwell designs, U.S. patent application Ser. No. 12/633,527 to Lake et al. also describes a feedwell with a single large opening disposed in its lower portion. Thus, this invention also suffers from the same undesirable turbulence and flow patterns that are induced in the sedimentation chamber as the other known systems.
U.S. patent application Ser. No. 12/745,891 to McElvenny also discloses a feedwell with a single large opening on its bottom. The apparatus disclosed in this application, however, attempts to mitigate the disturbance to the liquid in the sedimentation chamber by placing a conical plate directly below the outlet of the feedwell so as to spread out the flow of fluid exiting the feedwell into a larger ring-shape. However, even this proposed solution does not distribute the outflow of the feedwell over a significant area, because the very plate itself blocks a significant area below the flow in which some of the outflow could travel.
Other systems have also been developed which seek to make the outflow of the feedwell more uniform by incorporating a flow-shaping zone near the single large outlet of the feedwell. However, the result is still substantially the same—the entire outflow of the feedwell is concentrated in a single entry point in the sedimentation chamber, thus inducing turbulence in the contents of the sedimentation chamber.
There is thus a present need for a method and apparatus which provides a feedwell that distributes the outflow of the feedwell into the sedimentation chamber over a vastly large area so as to minimize turbulence in the contents of the sedimentation chamber.